Stroke is a leading cause of long-term disability, and motor impairment is the most common deficit post-stroke. Transcranial direct current stimulation (tDCS) shows promise in modulating cortical excitability to improve motor outcome in stroke patients. However, several questions about the parameters of this technique remain unclear, including the optimal current level and electrode montage for stroke patients. Determining these parameters is an important prerequisite for developing a clinical trial to assess the efficacy of this technique. This proposal aims to optimize these two parameters. We will first determine the optimal current between 1 mA to 4mA that balances the increase in cortical excitability and safety/tolerability. Once the optimal current level is determined, we will test 3 different types of electrode montages at that level to determine the optimal electrode montage that induces the maximal cortical excitability on the lesional motor cortex: 1) Anodal stimulation on the lesional motor cortex 2) Cathodal stimulation on the non-lesional motor cortex 3) Bi-hemispheric stimulation with anodal stimulation on the lesional motor cortex and cathodal stimulation on the non-lesional motor cortex This proposal serves as an important bridging step between the applicant's prior training and his next milestone - a Phase II single-center clinical trial (ROI application) to assess the efficacy of tDCS for stroke motor recovery utilizing the optimal current and stimulation montage determined by this proposal.